Water & Wastewater Treatment Magazine
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28 | XXXXX 20XX | WWT | www.wwtonline.co.uk The Works Trenchless technology Slip lining involves placing a smaller pipe inside the existing pipe. The Kobus Pipe Puller, which involves pulling out the old pipe and towing in a replacement, has also become a well-established option and recently won an innovation award at the NASTT No Dig Show in Chicago. If the replacement pipe needs to be slightly larger, pipe bursting – where the old pipe is forced into the surrounding ground – might be used. If a new pipeline route is required, though, there may be a need for impact moling or directional drilling, but those ap- proaches carry greater risk of utility strikes. "If you're doing something like slip lining, that's relatively straightforward," Ambler-Shattock says. "Laying the new services is where it gets more complicated. "We're working with various under- ground detection mechanisms and we've done a few jobs in this respect where we've been able to successfully utilise horizontal directional drilling techniques when people said it couldn't be done. It's not a question of whether it can't be done – it's a question of whether it might be too difficult for most contractors, or potentially carry too much risk due to extraneous factors. If you hit un- exploded World War II ordnance and cause an explosion in the middle of London, you've got a very big problem..." In the right conditions, techniques such as directional drilling are generally highly cost-effective and time-efficient when laying new mains pipes or cables, and work is tak- ing place that could open the door to more widespread use. The Government has announced that its Geospatial Commission is working to bring together the existing data on underground pipes and cables to create a UK-wide digital map, building on recent work by North- umbrian Water and Ordnance Survey in Sunderland. Detection technologies also continue to improve, with various solutions being explored. "We invest a lot in R&D and we're look- ing at how you can apply lidar, radar and ultrasonic techniques," Ambler-Shattock says. "We're at the early stages – it's still a little bit Heath Robinson, developing and putting together things that we find work in certain environments. "The big struggle has always been if you have a plastic pipe with something nasty running through it and it doesn't get picked up on any sort of radar. Unless there's a trace wire to identify it, you might find it the hard way." He adds: "You haven't yet got the shiny box that solves it all. We're probably about 10 years away from a situation where a worker pulls up in a van, fully detects what's in the area, the drilling commences and there are no nasty surprises." Exploring options While installing new pipelines into the most congested areas remains problematic, it is invariably worth considering how trench- less might play a role in any major pipeline installation or replacement programme. Engaging with experts at the earliest possible stage is key. While the terrain might demand that some sections are best carried out using traditional trenching, that doesn't mean trenchless can't be used for other sections. Mark Walters, director and water design engineer at UDS Utility Design Solutions, says using trenchless technologies over open-cut tends to save around £100 a metre, with slip lining representing the cheapest option, followed by pipe bursting and horizontal directional drilling. "You've got a hierarchy," he says. "First, does that water main need to be structur- ally renovated, i.e. replaced? Next, can it be downsized, so can you insert a smaller diameter pipe inside it? If not, you look at pipe-bursting. "In relatively urbanised areas where you have a lot of utilities crossing, that would hinder pipe-bursting because you have the potential to damage the adjacent utilities and you'd have to expose those utilities to be absolutely sure you're not going to impact on them, which increases the cost. "If not pipe-bursting, we'd look at direc- tional drilling. We're doing some projects in Bristol where there are residential areas but a limited amount of service connections. We've taken trial holes and proved that horizontal directional drilling is practicable. "We're basically trying to disprove trenchless technologies, working our way through that process, and as a last resort we'll open-cut. You always have to look at the most economical solution." Many in the water industry have recog- nised the potential for some time. Walters has worked as a water design engineer since 1991 and says trenchless has been used as the first consideration for most of that time. Drain also points out that numer- ous water companies have successfully adopted a range of no-dig technologies over the last couple of decades, and that in many cases these technologies have become the default options. However, the sector does still find itself significantly behind gas in its utilisation of trenchless. "Unfortunately, while the water industry does have genuine ambitions to innovate, the pace of adoption is painstakingly slow, resulting oŸen in new technologies being consigned to the corner of a warehouse rather than being utilised and hurdles overcome along the development path," Drain says. 28 | JUNE 2019 | WWT | www.wwtonline.co.uk The Kobus Pipe Puller requires only small excavation pits to remove and replace pipes K M Plant regularly uses techniques such as directional drilling to avoid road closures